The present invention relates to the field of mass storage devices. More particularly, this invention relates to an actuator of a disc drive.
One key component of any computer system is a device to store data. Computer systems have many different places where data can be stored. One common place for storing massive amounts of data in a computer system is on a disc drive. The most basic parts of a disc drive are a disc that is rotated, an actuator that moves a transducer to various locations over the disc, and electrical circuitry that is used to write and read data to and from the disc. The disc drive also includes circuitry for encoding data so that it can be successfully retrieved and written to the disc surface. A microprocessor controls most of the operations of the disc drive as well as passing the data back to the requesting computer and taking data from a requesting computer for storing to the disc.
The transducer is typically placed on a small ceramic block, also referred to as a slider, that is aerodynamically designed so that it flies over the disc. The slider is passed over the disc in a transducing relationship with the disc. Most sliders have an air-bearing surface (xe2x80x9cABSxe2x80x9d) which includes rails and a cavity between the rails. When the disc rotates, air is dragged between the rails and the disc surface causing pressure, which forces the head away from the disc. At the same time, the air rushing past the cavity or depression in the air bearing surface produces a negative pressure area. The negative pressure or suction counteracts the pressure produced at the rails. The slider is also attached to a load spring which produces a force on the slider directed toward the disc surface. The various forces equilibrate so the slider flies over the surface of the disc at a particular desired fly height. The fly height is the distance between the disc surface and the transducing head, which is typically the thickness of the air lubrication film. This film eliminates the friction and resulting wear that would occur if the transducing head and disc were in mechanical contact during disc rotation. In some disc drives, the slider passes through a layer of lubricant rather than flying over the surface of the disc.
Information representative of data is stored on the surface of the storage disc. Disc drive systems read and write information stored on tracks on storage discs. Transducers, in the form of read/write heads attached to the sliders, located on both sides of the storage disc, read and write information on the storage discs when the transducers are accurately positioned over one of the designated tracks on the surface of the storage disc. The transducer is also said to be moved to a target track. As the storage disc spins and the read/write head is accurately positioned above a target track, the read/write head can store data onto a track by writing information representative of data onto the storage disc. Similarly, reading data on a storage disc is accomplished by positioning the read/write head above a target track and reading the stored material on the storage disc. To write on or read from different tracks, the read/write head is moved radially across the tracks to a selected target track. The data is divided or grouped together on the tracks. In some disc drives, the tracks are a multiplicity of concentric circular tracks. In other disc drives, a continuous spiral is one track on one side of a disc drive. Servo feedback information is used to accurately locate the transducer. The actuator assembly is moved to the required position and held very accurately during a read or write operation using the servo information.
An actuator is used to move the read/write head or transducer. A voice coil motor is used to move the actuator. In most disc drives, the coil of the voice coil motor is attached to the actuator assembly. In most disc drives, the coil is attached to a y-shaped yoke. The an adhesive is typically used to attach the voice coil to the yoke. As the form factors for disc drives have been reduced, the size of the actuator and the yoke has also gotten smaller. In addition, the actuators within a form factor have also been made smaller and lighter to reduce the moment of inertia associated with the actuator. As disc drives have become smaller and smaller, the bonding surfaces between the voice coil and the actuator yoke have decreased which in turn has reduced the overall strength of the bond. Inadequate bonding causes other problems which result in failure of the disc drive. The bonding surface associated with the yoke of the actuator assembly can crack or the voice coil can separate from the yoke. When the voice coil separates, the voice coil is inoperable and the transducer attached to the actuator assembly can not be moved from track to track. Particles are also generated when the voice coil is separated from the yoke or when the crack in the yoke forms.
What is needed is a disc drive which allows for a smaller, lighter yoke but which has a sufficient bond strength to prevent separation of the voice coil from the yoke. Also needed is a design which prevents cracks form developing during temperature variation in the disc drive.
An actuator assembly for a disc drive includes a main body. A pivoting portion is included in the main body. The actuator assembly also includes an actuator arm attached to the main body and a yoke attached to the main body. The yoke has a roughened bonding surface. A voice coil is bonded to the yoke. The roughened bonding surface on the yoke can be accomplished using several different structures. The bonding surface may have a plurality of grooves therein. The bonding surface may include a plurality of lands. The bonding surface may include a plurality of raised portions. The bonding surface may also be provided with a first set of grooves and a second set of grooves. The first set of grooves would be transverse to a second set of grooves. The bonding surface may also have an elongated groove therein. The elongated groove would traverse the width dimension of the yoke. The bonding surface basically includes a plurality of features for increasing the area of the bonding surface between the yoke and the voice coil. The plurality of features in the bonding surface are designed to minimize cracks in the yoke of the actuator assembly.
Also disclosed is a method for attaching a voice coil to the yoke of an actuator assembly a disc drive. The voice coil is part of a voice coil motor for moving the actuator assembly. The method includes roughening the bonding surface of the yoke, applying an adhesive to one of the voice coil or the bonding surface, and placing the voice coil into contact with the bonding surface of the yoke. Roughening the bonding surface of the yoke may include providing features in the bonding surface of the yoke that increase the surface area of the bonding surface. Roughening the bonding surface of the yoke also may include providing features in the bonding surface of the yoke that decrease cracking in the bonding surface of the yoke. Specifically, roughening the bonding surface of the yoke includes forming grooves in the bonding surface of the yoke. Both a first set of grooves and a second set of grooves can be formed in the bonding surface of the yoke. When formed, the first set of grooves is transverse to the second set of grooves.
A disc drive actuator assembly includes a main body. The actuator assembly also includes a transducer. The transducer is attached to the main body. A yoke is also attached to the main body. The yoke includes a feature or features for increasing the surface area. Advantageously, the disc drive with the yoke having increased surface area allows for a smaller, lighter yoke with a sufficient bond strength to prevent separation of the voice coil from the yoke. The yoke design also prevents cracks form developing during temperature variation in the disc drive. The yoke and the disc drive last longer since a failure mode has been removed. In addition, the disc drive is more dependable over its extended life.